Experimental investigation of temperature on the physical and mechanical properties of red sandstone

Abstract

With the rapid development of transportation in China, the number of tunnels, as the main control project, is also increasing. However, tunnels may suffer from fire accidents during operation, and the surrounding rock of tunnels will be irreparably damaged by high temperature. To investigate the influence of temperature on the physical and mechanical properties of red sandstone, physical properties as well as Brazilian splitting test were conducted on red sandstone after thermal treatment from 25 ℃ to 600 ℃. The results show that with the increasing temperature, the apparent color of red sandstone is gradually deepened. The P-wave velocity and Leeb hardness decreased with the increase of temperature, and typical temperature threshold (300 ℃) was identified. The tensile strength of red sandstone decreasing quickly from 25 ℃ to 300 ℃ and then decreases slowly from 300 ℃ to 600 ℃. The acoustic emission (AE) signal has a high degree of consistency with the stress time curve. As the temperature increased, the AE became more active, when red sandstone is near to failure, the AE signal increases sharply. The failure mode of sandstone is mainly composed of a through main crack and a secondary crack, and the crack width also grows gradually. Moreover, we observe that the number of fractures in the sandstone also increase as the temperature rise by polarized light microscopy images. The variation of physical and mechanical properties of red sandstone is closely related to microstructure. These findings demonstrate that temperature has an obvious weakening effect on the physical and mechanical properties of sandstone, and provide theoretical guidance and engineering significance for tunnel fire restoration. Thematic collection: This article is part of the Engineering Geology and Hydrogeology of the Anthropocene collection available at: https://www.lyellcollection.org/topic/collections/engineering-geology-and-hydrogeology-of-the-anthropocene